package com.joy.zebra.handler;

import org.springframework.boot.web.reactive.error.ErrorWebExceptionHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.gateway.route.Route;
import org.springframework.cloud.gateway.support.NotFoundException;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.codec.HttpMessageReader;
import org.springframework.http.codec.HttpMessageWriter;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.util.Assert;
import org.springframework.web.reactive.function.BodyInserters;
import org.springframework.web.reactive.function.server.RequestPredicates;
import org.springframework.web.reactive.function.server.RouterFunctions;
import org.springframework.web.reactive.function.server.ServerRequest;
import org.springframework.web.reactive.function.server.ServerResponse;
import org.springframework.web.reactive.result.view.ViewResolver;
import org.springframework.web.server.ResponseStatusException;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


public class JsonExceptionHandler implements ErrorWebExceptionHandler {

	private static final Logger log = LoggerFactory.getLogger(JsonExceptionHandler.class);

	/**
	 * MessageReader
	 */
	private List<HttpMessageReader<?>> messageReaders = Collections.emptyList();

	/**
	 * MessageWriter
	 */
	private List<HttpMessageWriter<?>> messageWriters = Collections.emptyList();

	/**
	 * ViewResolvers
	 */
	private List<ViewResolver> viewResolvers = Collections.emptyList();

	/**
	 * 存储处理异常后的信息
	 */
	private ThreadLocal<Map<String, Object>> exceptionHandlerResult = new ThreadLocal<>();

	/**
	 * 参考AbstractErrorWebExceptionHandler
	 *
	 * @param messageReaders
	 */
	public void setMessageReaders(List<HttpMessageReader<?>> messageReaders) {
		Assert.notNull(messageReaders, "'messageReaders' must not be null");
		this.messageReaders = messageReaders;
	}

	/**
	 * 参考AbstractErrorWebExceptionHandler
	 *
	 * @param viewResolvers
	 */
	public void setViewResolvers(List<ViewResolver> viewResolvers) {
		this.viewResolvers = viewResolvers;
	}

	/**
	 * 参考AbstractErrorWebExceptionHandler
	 *
	 * @param messageWriters
	 */
	public void setMessageWriters(List<HttpMessageWriter<?>> messageWriters) {
		Assert.notNull(messageWriters, "'messageWriters' must not be null");
		this.messageWriters = messageWriters;
	}

	@Override
	public Mono<Void> handle(ServerWebExchange exchange, Throwable ex) {
		/**
		 * 按照异常类型进行处理
		 */
		HttpStatus httpStatus;
		String body;
		if (ex instanceof NotFoundException) {
			httpStatus = HttpStatus.NOT_FOUND;
			body = "Service Not Found";
		} else if (ex instanceof ResponseStatusException) {
			ResponseStatusException responseStatusException = (ResponseStatusException) ex;
			httpStatus = responseStatusException.getStatus();
			body = responseStatusException.getMessage();
		} else {
			httpStatus = HttpStatus.INTERNAL_SERVER_ERROR;
			body = "Internal Server Error";
		}
		/**
		 * 封装响应体,此body可修改为自己的jsonBody
		 */
		Map<String, Object> result = new HashMap<>(2, 1);
		result.put("httpStatus", httpStatus);
		result.put("body", body);
		/**
		 * 错误记录
		 */
		ServerHttpRequest request = exchange.getRequest();
		log.error("[全局异常处理]异常请求路径:{},记录异常信息:{}", request.getPath(), ex.getMessage());
		/**
		 * 参考AbstractErrorWebExceptionHandler
		 */
		if (exchange.getResponse().isCommitted()) {
			return Mono.error(ex);
		}
		exceptionHandlerResult.set(result);
		ServerRequest newRequest = ServerRequest.create(exchange, this.messageReaders);
		return RouterFunctions.route(RequestPredicates.all(), this::renderErrorResponse).route(newRequest)
				.switchIfEmpty(Mono.error(ex))
				.flatMap((handler) -> handler.handle(newRequest))
				.flatMap((response) -> write(exchange, response));

	}

	/**
	 * 参考DefaultErrorWebExceptionHandler
	 *
	 * @param request
	 * @return
	 */
	protected Mono<ServerResponse> renderErrorResponse(ServerRequest request) {

		Map<String, Object> error = new HashMap<>(3);

		Route gatewayRoute = (Route) request.attribute("org.springframework.cloud.gateway.support.ServerWebExchangeUtils.gatewayRoute")
				.get();

		error.put("code", 1);
		error.put("msg", gatewayRoute.getId() + " 模块未启动");
		error.put("data", false);

		Map<String, Object> result = exceptionHandlerResult.get();
		return ServerResponse.status((HttpStatus) result.get("httpStatus"))
				.contentType(MediaType.APPLICATION_JSON_UTF8)
				.body(BodyInserters.fromObject(error));
	}

	/**
	 * 参考AbstractErrorWebExceptionHandler
	 *
	 * @param exchange
	 * @param response
	 * @return
	 */
	private Mono<? extends Void> write(ServerWebExchange exchange,
			ServerResponse response) {
		exchange.getResponse().getHeaders()
				.setContentType(response.headers().getContentType());
		return response.writeTo(exchange, new ResponseContext());
	}

	/**
	 * 参考AbstractErrorWebExceptionHandler
	 */
	private class ResponseContext implements ServerResponse.Context {

		@Override
		public List<HttpMessageWriter<?>> messageWriters() {
			return JsonExceptionHandler.this.messageWriters;
		}

		@Override
		public List<ViewResolver> viewResolvers() {
			return JsonExceptionHandler.this.viewResolvers;
		}

	}

}
